I went from being pretty flexibly(ie pamls to floor) to touching my knee to my chest in under 5 minutes. This is kind of lengthy so bear with me.
Stretching is not so much a limitation of our physical bodies but one of our nervous system and a means of protection.
Im a tad rusty in the terminolgy so I will try to explain what I mean best I can, please bear with me. There are two things to consider when stretching, speed of movement and strength in a given position.
To overcome limitations in regard to speed (speaking just for legs now, but principle applies to all joints) you can increase flexibility by forcibly propelling your limb. An example would be doing straight leg kicks, keep the knee locked and simply pivot at the hip with some force and let your leg stop itself. You will notice that with each kick your foot goes slightly higher. While this is good and addresses one factor there is still another to consider.
In order to truely be flexible you need strength at the outer limits of your flexability. Weight resistance is good, but do to the extreme range of motion often needed to do the splits for example, there simply arent any machines(or few) that would work.
Isometrics done at every increment in a limbs range of motion can build strength and also overcomes the nervous systems limitations. Its hard to explaine, but bear with me and I will try my best. For this first example, lets just use the standard splits, one leg forward the other leg back. We have muscles both in the front of the thigh as well as the hamstring that limit movement so the stretch need to be perfromed once with one leg forward, other back and vice versa.
Chances are if you are like most guys you wont get very close to the floor at first and its ok if your back leg is on the knee, we are going to just concentrate on the front leg for now. With the front leg out, heal on the floor. This is best done on a wood or tiles floor with a cloth for padding under the heal as well as to allow it to slide out away from you easer. It is often nice to have a chair on either side of you to place your arms on to hold you up, when you first start your often not limber enough to have hands on the floor for support without leaning way forward.
Now, with all your might, press the heal of your front foot into the floor, contracting your glutes etc. Do this as hard as you possibly can for about 15 seconds and then relax, if your doing it right your foot should actually slide forward and your hips should lower as you relaxe. Continue this a few times or until you simply get tired. You whould actually gain many many inches of additional flexibility just from one sitting as will be noticed as your foot slides away when you relax. Its also imortant to keep your hips square and inline with your shoulders facing straight ahead. When done, switch sides and work the other leg.
Now, for the "chinese" splits (ie legs straight out to the sides) you essentially do the same thing. It works well if you can have a chair in front of you to support your torso upright. towels/rags under heals so the slide and for padding, toes pointed straight ahead, not up in the air. Lower yourself down until your stopped by your own body tensing. Now, once again with all your strength press both feet into the floor and keep pressing with all your might for 15 seconds and relax, as you relax, you should noticbly drop to a much lower position than when you started. Repeat this until exhausted or you hit the floor.
Do this 2x per week and if you are diligent you should be able to hit the floor in under 8 weeks.
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